Based on the definition of fractional Fourier transform (FRT), the propagation properties of an anomalous hollow beam (AHB) through the FRT have been investigated in detail. An analytical formula is ...derived for the FRT of an AHB. By using the derived formula, the properties of an AHB in the FRT plane are illustrated numerically. The results show that the properties of an AHB in the FRT plane are closely related to the parameters of the beam and the fractional order p. The derived formula provides an effective and convenient way for analyzing and calculating the FRT of an AHB.
A glassy phase with glass transition (GT) was formed in a wide B content range of 12–31 at% for (Co0.75Cr0.125Mo0.125)100-xBx alloys. The appearance of GT at the low metalloid content of 12%B among ...Co-, Fe- and Ni-based alloys is the first, in contrast to the absence of GT for (Fe0.75Cr0.125Mo0.125)88B12 and (Ni0.75Cr0.125Mo0.125)88B12 alloys. The Co-based 12%B glassy alloy crystallized through unique three stages, i.e., glass (G) → G + hcp + fcc → G + fcc → fcc + M23B6. The appearance of GT is due to the necessity of long-range rearrangement of constituent elements for the simultaneous precipitation of hcp and fcc phases from glassy phase. The glass transition temperature, crystallization temperature, Vickers hardness (Hv) and Young's modulus for the Co-based glassy alloys increase linearly with increasing B content and reach 904 K, 946 K, 1566 and 188 GPa, respectively, at 31%B. The good bending plasticity is retained up to 29%B. The crystallization of the 27–29%B alloy occurs through G → G + M23B6 → M23B6 + M2B and the ultrahigh Hv above 2000 is attained for the metastable G + M23B6 phase state. The glassy alloy rod with a diameter of 1 mm was prepared for the 27%B alloy and exhibited ultrahigh yield strength of 4700 MPa, plastic strain of 1% and high oxidation resistance up to about 1200 K. The Co-based bulk glassy alloy with simultaneously high strength, ultrahigh hardness and high oxidation resistance, is promising for the future high hardness and heat-resistance materials.
A new power-exponent-phase vortex beam with nonlinear phase winding has shown flexible control freedom compared with conventional vortex beams. In order to further enrich the modulation freedom and ...expand the ability of self-healing to meet current application requirements, we conducted a detailed study on the characteristics of the Airy transform of the new power-exponent-phase vortex beam. The influences of the Airy function, the power exponent, and the topological charge on normalized intensity and phase distributions are investigated theoretically and experimentally. More importantly, the self-healing properties of the new power-exponent-phase vortex beam with and without the Airy transform are compared. This shows that the new power-exponent-phase vortex beam with the Airy transform exhibits better self-healing ability when obstructed by obstacles. This study has potential applications in optical trapping and free-space optical communication.
We study the problem of coupling partially coherent radially polarized (PCRP) vortex beams into a single-mode optical fiber. Using the well-known concept of the cross-spectral density (CSD) matrix, ...we derive a general expression for the coupling efficiency of the partially coherent beam into a single-mode fiber. We adopt PCRP vortex beams for incident beams and use our general results to discuss the effects of the coherence, topological charge, and wavelength on the coupling efficiency of an optical beam focused onto a single-mode fiber with a lens. Our results should be useful for any application that requires coupling of partially coherent beams into optical fibers.
To clarify the effect of small magnetic fields on the magnetic properties and microstructure in FeCoSiBPC amorphous alloys, a magnetic field with different directions and various intensities was ...applied. The results show that the static field in orthogonal directions could all decrease Hc. Small fields like 50 Oe are also effective in reducing the Hc. The microstructure of the samples annealed with and without field were compared to figure out the effect of the magnetic field on the Hc. A change in the crystallization growth between field heat treated samples and non-field heat treated samples is observed where the field initially hinders crystallization to accelerate it at longer times. Small magnetic fields could also affect the proportion of bcc-Fe(Co) phase with different Co coordination number and are effective in aligning the magnetic domain, which could result in lower Hc by sweeping pinning site. The magnetic softening and magnetic hardening mechanism are also discussed.
This paper reports on the preparation of Fe82.7-85.7Si2-4.9B9.2-11.2P1.5.2.7C0,8 soft magnetic amorphous alloys with a distinctly high Fe content of 93.5-95.5 wt.% by component design and composition ...adjustment. All alloys can be readily fabricated into completely amorphous ribbon samples with good surface quality by the single copper roller melt-spinning method. These alloys show good bending ductility and excellent magnetic properties after annealing, i.e., low coercivity （He） of 3.3-5.9 A/m, high permeability （μe） of 5000-10000 and high flux saturation density （Bs） of 1.63-1.66 T. The mechanism of the good glass forming ability （GFA）and soft-magnetic properties are explored. The amorphous alloys with the high Fe content comparable to that of the desired high Si alloy can be promising candidates for the potential application in electric devices.
We report on a partially coherent power-exponent-phase vortex beam (PC-PEPV), whose spatial coherence is controllable and the initial phase exhibits a periodic power exponential change. The PC-PEPV ...beam was generated experimentally with various spatial coherence widths, and its propagation properties were studied both numerically and experimentally. By modulating the topological charge (TC) and power order of the PC-PEPV beam, the structure of the vortex beam can be adjusted from circular to elliptic, triangular, quadrangle, and pentagon. When the power order is odd, the PC-PEPV beam with a negative TC can be generated, and the profiles of the PC-PEPV beam can be precisely controlled
via
adjusting the value of the power order. For the case of high spatial coherence width, the number of the dark cores in the polygonal intensity array of the PC-PEPV beam equals the magnitude of the TC. However, when decreasing the spatial coherence width, the dark cores vanish and the intensity gradually transforms into a polygonal light spot. Fortunately, from the modulus and phase distributions of the cross-spectral density (CSD), both the magnitude and sign of the TC can be determined. In the experiment, the modulus and phase distribution of the CSD are verified by the phase perturbation method. This study has potential applications in beam shaping, micro-particle trapping, and optical tweezers.
By expanding the hard-aperture function into a finite sum of complex Gaussian functions, we derive approximate analytical formulae for Lorentz and Lorentz–Gauss beams propagating through an apertured ...fractional Fourier transform (FRT) optical system. As an application example, properties of a Lorentz–Gauss beam in the FRT plane after propagating through a squarely or annularly apertured FRT optical system are studied numerically. The results obtained using the approximate analytical formula are in good agreement with those obtained using numerical integral calculation. The FRT optical system provides a convenient way for laser beam shaping.
A new(Fe0.76Si0.09B0.1P0.05)98.25Nb1Cu0.75 bulk nanocrystalline alloy in a rod shape with a diameter of 2.5 mm was successfully developed by copper mold casting and isothermal annealing. It was found ...that the introduction of Cu can result in the formation of a large number of α-Fe(Si)clusters(less than 3 nm) embedded in the glassy matrix, which greatly improved the primary crystallization of α-Fe(Si) nanocrystals during subsequent annealing. The obtained superior soft magnetic properties can be ascribed to the formation of optimal nanocomposite structures with a large number of α-Fe(Si) nanocrystals( 17 nm) uniformly distributed in the glassy matrix.
The C-repeat-binding factors/DRE-binding factors (CBF/DREBs) comprise a key transcription factor family involved in plant stress tolerance. Yet, there is limited information about switchgrass DREB ...genes and their functional roles.
In this study, four cold-inducible
were identified from switchgrass (
), among which
was the one responded to cold stress later than the other three
. Yet, ectopic overexpression of
led to significantly compromised, instead of improved cold tolerance in transgenic tobacco. On the other hand,
was transcriptionally down-regulated in response to salt stress, but overexpression of
improved plant salt tolerance in transgenic tobacco. The improved salt tolerance was associated with increased K
/Na
ratio and Ca
content, higher cellular osmotic potential, and activation of stress-related functional genes in the leaves of transgenic plants under salt stress.
The current results implied that
played opposite roles in plant cold and salt tolerance. Although DREB1s were known as positive stress regulators, particular attentions shall be paid to their potential negative regulatory role(s).
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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